1. Field of the Invention
The invention relates to a rehabilitation aid in the form of a treadmill whose belt speed is set to a patient""s own step cycle based on leg length or step length. The treadmill helps rehabilitation of stroke, spinal cord, head injury, amputees, orthopedic, neurologic and vestibular patients by improving their gait characteristics, step frequency and stride length to match the user""s own step cycle as a function of leg length or step length.
2. Discussion of Related Art
U.S. Pat. No. 5,623,944, entitled METHOD FOR CHARACTERIZING GAIT, issued Apr. 29, 1997 Nashner. This patent contains a description of the Categories of Gait and the characterization of Gait Using A Treadmill. The description is informative in describing the direction that the state of the art has taken and so is reproduced here.
The phases of human gait have been described by many authors; some examples include, Inman, et al. (1981) xe2x80x9cHuman Walking,xe2x80x9d Williams and Wilkins, Baltimore; Winter, D. A. (1983) xe2x80x9cBiomechanical Motor Patterns in Normal Walking,xe2x80x9d Journal of Motor Behavior 15:302-330; and Winestein, et al. (1989) xe2x80x9cQuantitative Dynamics of Disordered Human Locomotion: a Preliminary Investigation,xe2x80x9d (Journal of Motor Behavior 21:373-391). Human gait may be classified in general categories of walking and running. During walking, at least one foot is always in contact with the support surface and there are measurable periods of time greater than zero during which both feet are in contact with the support surface. During running, there are measurable periods greater than zero during which time neither foot is in contact with the support surface and there are no times during which both feet are in contact with the support surface.
Walking can be separated into four phases, double support with left leg leading, left leg single support, double support with right leg leading, and right leg single support. Transitions between the four phases are marked by what are generally termed xe2x80x9cheel-strikexe2x80x9d and xe2x80x9ctoe-offxe2x80x9d events. The point of first contact of a foot is termed a xe2x80x9cheel-strikexe2x80x9d, because in normal adult individuals the heel of the foot (the rearmost portion of the sole when shoes are worn) is usually the first to contact the surface. However, heel-strike may be achieved with other portions of the foot contacting the surface first. During running normal adult individuals sometimes contact a surface with the ball of the foot (forward portions of the sole when shoes are worn). Individuals with orthopedic and/or neuromuscular disorders may always contact the surface with other portions of the foot or other points along the perimeter of the sole when shoes are worn. Similarly, while the ball and toes of the foot are the last to contact the surface at a toe-off event in normal adults, a patient""s last point of contact may be another portion of the foot. Thus, regardless of the actual points of contact, the terms heel-strike and toe-off refer to those points in time at which the foot first contacts the support surface and ceases to contact the surface, respectively.
Treadmills allowing a subject to locomote over a range of walking and running speeds within a confined space have been described in the prior art (Traves, et al. (1983) xe2x80x9cA Speed-Related Kinematic Analysis of Overground and Treadmill Walkingxe2x80x9d; Winter, et al. (eds.) Biomechanics XI, Human Kinetics Publishers, Champaign, pp. 423-426; Nelson, et al. (1972) xe2x80x9cBiomechanics of Overground Versus Treadmill Running,xe2x80x9d Medicine and Science in Sports 4:233-240; and Charteris, et al. (1978) xe2x80x9cThe Process of Habitation to Treadmill Walking: a Kinetic Analysis,xe2x80x9d Perceptual and Motor Skills 47:659-666). A treadmill allows the difficulty of gait to be precisely set by independently controlling the belt speed and the inclination of the belt. The subject can be maintained in a fixed position relative to the measuring surface underlying the treadmill belt by coordinating the speed of gait with the speed of the treadmill belt movement. Several prior art research studies have described treadmills in which a single forceplate with mechanically coupled force transducers has been mounted directly beneath the treadmill belt. Kram et al., in their paper xe2x80x9cA Treadmill-Mounted Force Platformxe2x80x9d, Journal of The American Physiological Society, 1989, pages 1692-1698, describe a treadmill having a single forceplate. This paper is enclosed herewith and hereby incorporated herein by reference. The single forceplate provided continuous measurement of the forces exerted by the combined actions of the two feet on the overlying treadmill belt during gait.
It is sometimes desirable to determine the position of the center of force in relation to coordinates of specified anatomical features of the foot when the foot is in contact with a surface which is moving in relation to a fixed force sensing surface. This occurs, for example, when the foot is contacting the moving belt of a treadmill which overlays a force sensing surface. To determine the position of the center of force in relation to coordinates of the specified anatomical features of the foot, two coordinate transformations are performed. One, the position of the center of force is determined in relation to coordinates of the moving treadmill belt. Two, the position of the moving treadmill belt is determined in relation to coordinates of the specified anatomical feature of the foot. To perform the first of these coordinate transformations requires knowledge of the treadmill belt position in relation to the fixed force sensing surface position on a continuous basis. To perform the second of these two coordinate transformations requires knowledge of the position of the specified anatomical features of the foot in relation to the treadmill belt. Since the position of the foot and its anatomical features does not change in relation to the treadmill belt following each heel-strike event and before the subsequent toe-off of that foot, the position of the specified anatomical features of the foot needs to be determined only once at heel-strike for each step.
One method to determine the position of the treadmill belt on a continuous basis in relation to the fixed force sensing surface is to use one of several sophisticated commercial treadmill systems described in the prior art which measure the anteroposterior speed of the moving treadmill belt on a continuous basis, and which provide the means to regulate the belt anteroposterior speed on a continuous basis. One example of a commercially available treadmill system with automatic speed control and belt speed measurement systems is the Star Trac 2000, manufactured by Unisen, Inc., Tustin, Calif. When one of these treadmill systems is used, the information necessary to determine the continuous position of the treadmill belt in relation to the underlying forceplate is obtained by performing mathematical integration of the belt speed signal on a continuous basis.
There are methods described in the prior art which can be used to determine, at the time of heel-strike, the position of the moving treadmill belt in relation to the specified anatomical features of the foot. One method is to use one of several commercially available optical motion analysis systems. Two examples of commercially available motion analysis systems which describe applications for tracking the motions of identified points on the human body during locomotion include the ExpertVision system manufactured by Motion Analysis Corp., Santa Rosa, Calif. and the Vicon system manufactured by Oxford Medilog Systems, Limited, Oxfordshire, England. In accordance with this method, one or more optical markers are placed on the specified anatomical features of the foot. One or more additional markers are placed on the treadmill belt at predetermined positions. The number and placement of the optical markers on the anatomical feature and the treadmill belt determine the accuracy of the measurement as specified by the systems manufacturers. At the time of heel-strike, the positions of the treadmill belt marker or markers are then determined in relation to the positions of the anatomical feature marker or markers in accordance with methods specified by the system manufacturer.
U.S. Pat. No. 5,623,944 describes devices and methods for separately determining quantities related to the force exerted by each foot against the treadmill belt support surface at all phases of the step cycle and a means for determining quantities related to the position of the center of force exerted by each foot in relation to a fixed point on the treadmill belt or in relation to a specified anatomical feature of the foot or to train normals to alter their gait patterns. A method and apparatus for characterizing the gait of a subject is revealed that uses a treadmill having a movable support surface with multiple transducers mounted beneath the movable support surface. The subject performs locomotion on the movable surface. The computer accepts a series of signals from each transducer and identifies the occurrence of heel-strike and toe-off. The computer identifies the subject""s activity as walking or as running. The computer identifies two non-contiguous groups of transducers that are measuring a force greater than zero associated with the two feet and calculates quantities related to the forces exerted by each foot during each phase of walking or running.
The present inventors, however, have made some observations as follows under Gait Training.
One of the most evident indicators of overall health is gait speed. People with gait problems have unsymmetrical or shortened step lengths, and are typically stroke, spinal cord, head injury, amputees, orthopedic, neurologic or vestibular patients. Such patients may strive to attain normal walking patterns, but require improvement in their balance and coordination, strength and range of motion, and cardiovascular capacity and endurance.
There are two methods in which a patient can increase gait speed. One is to increase stride length and the other is to increase step frequency. Regardless of step length, people are most comfortable walking at a cadence of about 2 steps per second. The ideal step length may be determined by measuring the patient""s leg length.
Patients may have a wide stance shuffle. Such patients may assume that this gait pattern is not the result of weakness, but instead from a lack of confidence and a fear of falling. There is a need, therefore, to provide an environment that is safe and controlled that helps such patients regain that confidence.
Conventional treadmills must be set to a constant speed. There is no way to determine the user""s cadence at these speeds. Indeed, a comfortable walking speed will differ depending on the step length. To be considered a community ambulator, patients must walk at least 0.6 meters/second. This value is a guideline for functional independence. There is a need for an apparatus to evaluate a patient""s stride length, cadence, gait velocity and gait pattern and then provide quantified documentation so as to help such patients become a community ambulator.
Therapists who work with patients who require rehabilitation of their gait need to document important gait parameters of such patients so as to assess improvement over time. Clear, concise quantified documentation reinforces the benefits of therapy to the patient, healthcare providers and third party payers. Further, both the therapists and the patients need the rehabilitation process to take place in an environment that is safe to both.
It would be desirable to provide an apparatus and technique that fulfills all these needs by evoking the right stride length and step cycle for the patient using the apparatus.
One aspect of the invention resides in a treadmill whose belt speed matches a user""s own step cycle based on leg length or step length and which provides evaluation with respect to the user""s stride length, cadence, gait velocity and gait pattern. A pattern of ideal foot prints, which are shown in accordance with the user""s own step cycle, are scrolled on a display screen together with representation of foot falls that correspond to actual heel strike events on the treadmill.